Heat treating furnace



Nov. 8, 1966 J. KoTATKo ETAL HEAT TREATING FURNACE 4 Sheets-Sheet 1 Filed July 31, 1961 INVENTORS ci/Ka [as e7 .fma/e/O .fosef X1 0 Nov. 8, 1966 J. Ko'fATKo ETAL 3,

HEAT TREATING FURNACE Filed July 31, 1961 4 Sheets-Sheet 2 INVENTORS 7052 flaw/m, J w

BY Jm a/e C Nov. 8, 1966 J. KoiATKo ETAL 3,284,074

HEAT TREATING FURNACE Filed July 31, 1961 4 Sheets-Sheet 5 Nov. 8, 1966 J. KoiATKo ETAL 3,284,074

HEAT TREATING FURNACE Filed July 31. 1961 4 Sheets-Sheet 4 United States Patent 3,284,074 HEAT TREATING FURNACE Josef Kotatko and Josef mlek, Prague, Czechoslovakia, assignors to Zavody V.I. Lenina Plzen, narodni podnik, Plzen, Czechoslovakia Filed July 31, 1961, Ser. No. 128,101 Claims priority, application Czechoslovakia, Aug. 1, 1960, 4,835/ 60 7 Claims. (Cl. 266-) The present invention relates to heat treating furnaces and more particularly to furnaces using a protective at mosphere for scale-free heat treatment of metal objects. Such furnaces are used in the heat treatment of steel objects in order to maintain a clean surface or without decarbonizing the steel surface or for other heat treatment and hardening.

Heating is accomplished either by radiation from refractory elements or by immersion of the steel objects in a heated liquid. In any case heating is indirect and the steel material has to be protected from the combustion gases. The radiant refractory elements must be made of a heat resistant nickel chromium steel in order to withstand the high heating temperatures. The elements are expensive and their lifetime is shorter than that of thefurnace lining, and they increase the costs of furnace operation. In addition the heat of the combustion gases, which leave the heating elements at an elevated temperature is not efficiently used.

It is an object of this invention to provide a furnace having a protective atmosphere in which the heat supplied is efiiciently transmitted to the treated article. A further object is the prevention of direct contact of this article with the combustion products. Another object of this invention is the use of a gaseous medium, which reacts in a desired manner with the treated article.

With these and other objects in view, the invention in one of its aspects resides in a heat treating furnace the working space of which is defined by a floor and by walls which extend upwardly from the floor. The walls are formed with vertically elongated grooves laterally open toward the working space. Outlet ports communicate with respective portions of the grooves remote from the floor in an upward direction. Burners which produce combustion gases communicate with respective portions of the grooves adjacent the floor by means of orifices which face in the direction of groove elongation toward the corresponding outlet port.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 shows a heat treating furnace of the invention in front elevational section on the line I-I in FIG. 2;

FIG. 2 is a sectional plan view of the furnace of FIG. 1 taken on the line IIII;

FIG. 3 shows the furnace of FIG. 1 in side-elevational median section on the line IIIIII;

FIG. 4 is another side-elevational sectional view of the furnace of FIG. 1 taken on the line IVIV, with portions of the furnace structure broken away;

FIG. 5 shows the furnace of FIG. 1 in front elevational section of the line VV in FIG. 2; and

FIG. 6 shows a furnace of the invention modified to have a movable floor, the view corresponding to that of FIG. 1.

Referring to the drawing in detail, and initially to FIGS. 1 to 5, there is seen a furnace which comprises a working space 1. The lateral walls 2 of the furnace are provided with parallel ceramic heating grooves 3 of parabolic cross section extending from the bottom to the top of said space, and arranged along the entire length of the working space 1. The upper parts 4 of the lateral walls 2 and their grooves 3 are arched about an axis located at about three quarters of the maximum height of the object 18 to be heated. Thus the heat radiated by the upper part of the lateral wall 2 is concentrated on the upper surface of the heated object 18. The lower parts of the ceramic heating grooves 3 communicate with burners 6 mounted on the frame of the furnace; the orifice 7 of each burner 6 is substantially at the focus of the parabolic curvature of the corresponding ceramic heating groove 3. The hot combustion gases stream through each ceramic heating groove 3 towards a port 15 in the upper part of the heating groove which leads into a manifold outlet channel 8. The combustion gases passing along the groove heat its parabolic surface, which radiates heat toward the heated object 18. The combustion products are held in the ceramic heating groove 3 by their own momentum and by the pressure of the protective atmossphere within the working space 1. In the arched wall part 4 they are urged against the parabolic groove surface by centrifugal force. They are released through the out let port 15 at the top of each ceramic heating groove 3 without spreading into the working space 1. The gaseous protective atmosphere enters the working space l' ffom the top and from the bottom. A valved conduit 12 connects a source of the protective medium with a'central channel 10 which forms a preheating chamber at the top of the furnace and feeds the protective medium to the central upper part of the working space 1. The channel 10 is divided by a partition wall 11 in such a manner as to lengthen the heating path of the protective medium to ports 13 in the upper part of the working space 1, through which it is discharged in the direction towards the heated object 18. As the protective medium is preheated by the walls of the central channel 10, it does not cool the heated object 18. In order to achieve a circulation of the protective medium, an additional amount thereof is introduced into the working space 1 through lateral ports 17 arranged in the floor 21 opposite each ceramic heating groove 3. The protective medium is brought to the ports 17 through channels 16 in the lateral walls from channels 14 arranged adjacent the outlet channels 8. It enters the channel 14 from a valved supply conduit 20 and is heated during passage through the channel 14 and through the channel 16. The floor 21 is provided with transverse grooves 22 which connect the ports 17. The heated medium discharged upwardly from the lateral ports 17 draws the protective medium from the port 13 at the top of the working space 1 and transmits heat to the lower part of the object 18. The protective medium flows from the ports 17 along the ceramic heating grooves 3 and is heated thereby. A part of the medium is taken along by the stream discharged from the port 13 in the upper part of the working space 1, another part escapes through the outlet ports 15 in the upper part of the ceramic heating grooves 3 into the channel 8 where any residual combus'tible fractions are burned with air entering through ports 19 communicating with an air conduit 23. The combustion gases proceed furthermore into a flue 9 equipped with a recuperator 24 where they transmit a portion of their heat to the combustion air, for the burners 6 in a conventional manner, not illustrated in detail, in order to increase the efficiency of the furnace. The furnace floor 21 is heated by means of heating channels 25 connected to channels 27 in the rear wall, through which the hot combustion gases from burners 26 are passed. For furnaces with a mobile floor this heating is not required. The length of the working space 1 and the number of ceramic heating grooves 3 are selected according to the desired permformance of the furnace.

The object 18 is heated by radiation from the ceramic grooves 3. The grooves are heated to a high temperature by the combustion gases from the burners -6. The protective medium suppliedthrough the central channel to the ports 13 at the top of the working space 1 and through the lateral channels 14 and 16 to the lateral ports 17 in the lower part of the Working space 1 is heated before it circulates in the working space 1. It protects the heated object 18 from the combustion gases in the grooves 3. The working space 1 can be provided with a mobile floor 28 as shown in FIG. 6 which illustrates a furnace otherwise closely similar to that shown in FIGS. 1-5.

The furnace according to this invention permits the heat treatment of objects in a protective atmosphere without the use of heat radiating elements which have to be manufactured from costly material. The ceramic heating grooves withstand high temperatures, and their first cost is lower than that of radiating tubes, retorts and similar elements of highly alloyed metal. Their life time is longer, so that failures in operation are avoided. The fuel is better utilized, because the heating grooves operate at higher temperatures and radiate heat more intensively towards the heated objects. The time of heat treatment is thereby reduced. If a small amount of sealing is acceptable, it is possible to operate the furnaces of the invention without a protective atmosphere.

It should be understood, of course, that the foregoing disclosure relates only to preferred embodiments of the inventidfi, and that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purpose of the disclosure which do not constitute departures from the spirit and scope of the invention set forth in the appended claims.

We claim: v

1. A heat treating furnace comprising, in combination:

(a) floor means;

(b) wall means extending upward from said floor means, said floor means and said wall means jointly defining a working space therebetween, said wall means being formed with (1) a plurality of vertically elongated grooves laterally open toward said working space, and with (2) outlet port means directly communicating with a portion of each of said grooves remote from said floor means in an upward direction; and

(c) burner means for producing a combustion gas, said burner means including a plurality of conduits communicating with pcTrtions of respective grooves adjacent said floor means, each conduit having an orifice in the respective groove facing in the direction of elongation of said groove toward said outlet port means.

2. A furnace as set forth in claim 1, wherein said grooves have a substantially parabolic cross section flaring toward the open side of the grooves.

3. A furnace as set forth in claim 1, wherein said wall means includes a ceramic channel member formed with one of said grooves.

4. A furnace as set forth in claim 1, wherein said grooves have a substantially parabolic cross section flaring toward the open side of the groove, and said orifices are aligned with the respective foci of the parabolic cross sections of said grooves.

5. A furnace as set forth in claim 1, wherein said wall means include two walls having respective lower portions facing each other on opposite sides of said working space, said walls being formed with said grooves and having respective upper portions arcuately extending from said lower portions toward the upper portion of the other wall.

6. A furnace as set forth in claim 1, further comprising discharge means for discharging a protective gaseous medium into a portion of said Working space inwardly spaced from said grooves.

7. A furnace as set forth in claim 6, further comprising means for preheating said gaseous medium prior to discharge into said working space.

References Cited by the Examiner UNITED STATES PATENTS CHARLIE T. MOON, Primary Examiner.

RAY K. WINDHAM, F. R. LAWSON,

Assistant Examiners. 

1. A HEAT TREATMENT FURNACE COMPRISING, IN COMBINATION: (A) FLOOR MEANS; (B) WALL MEANS EXTENDING UPWARD FROM SAID FLOOR MEANS, SAID FLOOR MEANS AND SAID WALL MEANS JOINTLY DEFINING A WORKING SPACE THEREBETWEEN, SAID WALL MEANS BEING FORMED WITH (1) A PLURALITY OF VERTICALLY ELONGATED GROOVES LATERALLY OPEN TOWARD SAID WORKING SPACE, AND WITH (2) OUTLET PORT MEANS DIRECTLY COMMUNICATING WITH A PORTION OF EACH OF SAID GROOVE REMOTE FROM SAID FLOOR MEANS IN AN UPWARD DIRECTION; AND (C) BURNER MEANS FOR PRODUCING A COMBUSTION GAS, SAID BURNER MEANS INCLUDING A PLURALITY OF CONDUITS COMMUNICATING WITH PORTIONS OF RESPECTIVE GROOVES ADJACENT SAID FLOOR MEANS, EACH CONDUIT HAVING AN ORIFICE IN THE RESPECTIVE GROOVE FACING IN THE DIRECTION OF ELONGATED OF SAID GROOVE TOWARD SAID OUTLET PORT MEANS. 